Shadow Chancellor Ed Balls has said “we'll all miss him in Parliament" while David Lammy tweeted: “David Miliband a big loss to PLP [Parliamentary Labour Party].”

David Miliband has been a backbencher since losing the Labour leadership contest in 2010, something that shocked many people at the time because he was so widely considered to be one of the party's high-flyers - he was one of the youngest foreign secretaries Britain has ever had.

A by-election in South Shields shouldn't cause the Labour party too many problems - Miliband had a massive 18,995 majority.

The relationship between the brothers was a psychodrama of British politics. Credit: Stephen Hird / Reuters

There were many who saw him as the possible successor to his brother, Ed; to many he was a standard bearer of Blairite ideas and the right of the Labour party.

Tory MPs have seized on the announcement to accuse Labour of “lurching to the left”.